Gene variant identified in depression

One in every 10 people with major depression may carry a particular variant of a gene that makes it difficult to respond to most common antidepressant medicines, according to a new study.

Marc Caron and his colleagues at the Duke Institute for Genome Sciences and Policy have identified this so-called gene variant in nine of 87 patients studied.

All but two of the nine failed to get better on antidepressants. The remaining two patients benefited only at the highest dose, according to Caron, a researcher in the department of cell biology. The study was published last week in the online version of the journal Neuron.

"If this finding is replicated, we may be able to subtype depression and predict who should get specific treatments. It would be the beginning of personalized treatment," said Dr. Thomas Insel, director of the National Institute of Mental Health in Bethesda.

Major depression is believed to affect 20 million Americans. Studies have suggested that the brain chemical serotonin is at the heart of the debilitating problem. The most commonly prescribed drugs, selective serotonin reuptake inhibitors such as Prozac, put the brakes on the brain's serotonin transport system, a treatment that keeps the chemical inside brain cells for a longer period. This alleviates many symptoms of depression.

But this class of medicines doesn't work for everyone, and scientists have been trying to figure out why.

They discovered a gene mutation that alters an enzyme that affects serotonin levels. When they looked at 87 people with major depression, nine had the genetic variant. Insel said that this gene could predispose people to depression.